“The period of time occupied by organic intelligence is just a thin sliver between early life and the long era of the machines,” says Martin Rees is Emeritus Professor of Cosmology and Astrophysics, at the University of Cambridge, the Astronomer Royal, a member of Britain’s House of Lords, and a former President of the Royal Society. “Because such civilizations would develop at different rates, it’s extremely unlikely that we will find intelligent life at the same stage of development as us. More likely, that life will still be either far simpler, or an already fully electronic intelligence.”

“The question of whether advanced civilizations exist elsewhere in the universe has always been vexed with three large uncertainties in the Drake equation,” said University of Rochester astronomer, Adam Frank. “We’ve known for a long time approximately how many stars exist. We didn’t know how many of those stars had planets that could potentially harbor life, how often life might evolve and lead to intelligent beings, and how long any civilizations might last before becoming extinct.”

Estimates from NASA’s Kepler Mission data suggests that out of the estimated 2 x 10^22 stars in the known universe, 20 percent have planets that reside in habitable zones that have temperatures, atmospheres, and other traits that could support life. So that takes care of one uncertainty.

“Aliens could exist in forms we can’t conceive,” Rees says “They could be staring us in the face and we just don’t recognize them. The problem is that we’re looking for something very much like us, assuming that they at least have something like the same mathematics and technology.”